Some mobile devices include a positioning system, such as a Global Positioning System (GPS), to determine a user's current geographic location and display a map showing a marker for the user's current geographical location. As the user moves to a different location, the positioning system recalculates the current location of the user, and refreshes the displayed map to reflect the updated location of the user.
Some mobile devices also allow location-sharing among users who have agreed to become “location-sharing friends” with one another. For example, two users can register with a location information server and agree to share their geographical locations with each other. The location information server maintains a database of location information submitted by the respective mobile devices associated with the two users. The location information server will forward the location information of one user to the other user either upon request, on a schedule, or upon receiving a submission of a location update. Each user can view the location-sharing friend's location on a map displayed on the user's own mobile device.
To keep the location information stored in the location information database up-to-date, the location-sharing mobile devices periodically recalculate their respective current positions and submit location updates to the location information server. To submit periodic location updates to the location information server, a location-sharing mobile device has to maintain an active background process for location determination and update submission regardless of whether other devices request such up-to-date information from the location-information server. Maintaining such active background process consumes power and shortens battery life significantly even if the device is not otherwise in use.